How to calculate profit using aggregations from two collections in mongodb? - mongodb

Question

I have two collections, orders and producttypes
ProductTypes:
{
"_id" : 609d79de5909592f2635c64e,
"name" : "T-Shirt",
"subType" : "Round Neck",
"__v" : 0,
"size" : "XXL",
"sellingPrice" : 320,
"createdAt" : ISODate("2021-05-18T05:22:00.695+0000"),
"actualPrice" : 200,
"updatedAt" : ISODate("2021-05-25T12:11:50.986+0000")
},
{
"_id" : 609d79de5909592f2635c64d,
"name" : "T-Shirt",
"subType" : "V Neck",
"__v" : 0,
"size" : "XXL",
"sellingPrice" : 290,
"createdAt" : ISODate("2021-05-18T05:22:00.695+0000"),
"actualPrice" : 200,
"updatedAt" : ISODate("2021-05-25T12:11:50.986+0000")
}
Orders:
{
"_id" : "60a63e369cf3a806c0209bd8",
"items" : [
{
"type" : "609d79de5909592f2635c64e",
"quantity" : 1,
"sellingPrice" : 320
},
{
"type" : "609d79de5909592f2635c64d",
"quantity" : 2,
"sellingPrice" : 290
}
],
"orderId" : "ORD101",
"from" : "Abc",
"to" : "xyz",
"createdAt" : ISODate("2021-05-20T10:47:18.920+0000"),
"__v" : 0,
"tracking" : "12345678"
}
I want to calculate total profit per order like:
{orderId: "ORD101", createdAt: ISODate("2021-05-18T05:22:00.695+0000"), profit: 300}
I don't know how to join these two collections to calculate the profit.
But I tried something like below in node:
Order.aggregate([{
$unwind: '$items'
}, {
$project: {
orderId:1,
quantity: "$items.quantity",
sellingPrice: {
$multiply: [
{"$ifNull": ["$items.quantity", 0]},
{"$ifNull": ["$items.price", 0]}
]
},
type: '$items.type'
}
}])
.exec(function(err, transactions) {
//console.log(transactions);
ProductType.populate(transactions,{path: 'type', select: 'actualPrice' }, function(err, populatedTransactions) {
//res.json(populatedTransactions);
var items = [];
var totalProfit = 0;
if(populatedTransactions){
populatedTransactions.forEach( order => {
if( order.quantity != undefined && order.sellingPrice != undefined && order.sellingPrice > 0){
let profit = order.sellingPrice - (order.quantity * order.type.actualPrice);
totalProfit = totalProfit + profit;
items.push({ orderId: order.orderId, profit: profit });
}
})
res.status(200).json({data: items, totalProfit: totalProfit});
}
});
});
Is this the right way?
Here am using $unwind on the array then populating with producttypes collection to get an actual price, then am doing calculations to get the profit.

Answer 1

$project to show required fields
$unwind deconstruct the items array
$lookup with productTypes collection
calculate the profit
$arrayElemAt to get first element from item actualPrice result
$subtract sellingPrice by actualPrice
$multiply above result with quantity
$group by order _id and get required fields and sum profit
Order.aggregate([
{
$project: {
orderId: 1,
createdAt: 1,
items: 1
}
},
{ $unwind: "$items" },
{
$lookup: {
from: "productTypes", // replace your actual collection name
localField: "items.type",
foreignField: "_id",
as: "item"
}
},
{
$addFields: {
profit: {
$multiply: [
{
$subtract: [
"$items.sellingPrice",
{ $arrayElemAt: ["$item.actualPrice", 0] }
]
},
"$items.quantity"
]
}
}
},
{
$group: {
_id: "$_id",
orderId: { $first: "$orderId" },
createdAt: { $first: "$createdAt" },
profit: { $sum: "$profit" }
}
}
])
Playground